Recovery of tar acids



Oct. 13, 1942. c. M. AMBLER, JR A 2,298,816

RECOVERY oF TAR ACIDS vFiled Aug. 95,1939

` ATTORNEY Patented Oct. 13, 1942 2,298,816 RECOVERY oF 'initzicibs Cha'rlesM.` Ambler, Jr., Jenkintown, Pauassgm `or to The Sharples Corporation, Philadelphia; Pa., a corporation of Delaware Application August 9, 1939, soi'iol iso:- esatte 11 Claims.

The present inventior'ipertans tothe recovery of tar acids 'from' phenolate-:containing liquors derived from lcrude tar. It may loel regarded as an improvement of theV process of U; S. Eatent 2,081,692'-to 'Charles M. Ambler, Jr., 'and Charles E. nderwood. i v

In accordance with the process of U. S. Patent 2,081,692, crude tar is mixed with an alkali solu-l tion to effect reaction 'between vthe alkalifand `the phenolicconstituerits of the crude tar and solu; tion of the phenolate reaction products in the aqueous phase. The aqueous phase is thereafter separated fromthe crudeutar by centrifugation, sprung with an acid to `freel'fhe phenolicV cornpoundsf'and subjected 1 tov distillation fori recovery of these phenolic compounds. Such yafprocess "affords' an important advantage in the avoidancefof the distillation step-by` which a'- tar oil fraction has heen'V inst-separated from crude* tar' in the practice of4 theprior art before treatment of this tar oil fractionseparately4 for recovery of vpheencountered inigconnectio'nA with theip'rocess of Patent` 2,081,692, however, andanV object of thel be` sprung by treatment with! carbon4 dioxide.l

When sulfuric aloiddi's used as thefspringing agent, the` alkaltfifeed'by theMVM springing step combines with the sulfuric acid to form tiieJaIKalimetal salt" of the A springing-v acidl (sodium sulfate) and this alkali metal salt has'practically-no" value.y

When carbon dioxideis used asl the springing agent; the ltari` acidsderived from the springing step and subsequent distillation arerelatvely ini-'- pura-r and? the' tar'` acid fraction obtained by springing. and distillation hasy hydrophilic? propertiesyindicating: thatthe-tar acids haveriot' been adequately-puried. They contain an undesirably-A high proportio'nilo ash, and` this is anl indication that the Aseparation of l the alkali fromfthe phenolates. in-:the springing vstep is incompletek Regardless of whether the springingy step-isaecomplished; by'l carbon `dioxide or` by sulfuric acid in: the practice off the 'process of- Patent 2,081,692, a coke'-likeresiduefisl formed" the still? incident to distillation, rendering continuous' distillation impossible, and introducing di'iculties connection with the removaloi` this re's'idue-evenfmcases inwhich the distillation` is:` accomplished b'yF-batch operation.

An object of the present inveritinL has been` (o1. zenuw) t to o'ooo"toplistn uiespritgiiig onu purification of the phen late] nbr! obtained in the pija'cticeof Patent 2,081;692 `1n "such a way 'as to avoid all'of me above=mntioiiedeinooities; Y p v i Further yobectls` and aivantagesjof the invention;` and the manner' in Vwhich they have jbeen attained; will be evident from` a Yreading of the iouoofig spcification 'in io'rimotionA with the attachedowshetrin which the single figure is a difagiaininatic representation o`f oneexnbodi- 3 theintfention; Y l

i .v/ing? by reference characinfs'olutiri (p ferably sodiunfili'ya 'iter assumed to he suchal'- oom cion reagents. may-bos'ed) from ted'with# taf from `tank vI` I in fr' of yac'lueous` phenolate` soobtainedv as a` result of lfz-, is-noxt passed tov4 a ZeiltrifiigaflE separator |-3,-` rand the equeou's phenol'a'te solution is ntiuusly separated froin the crude tar by the centrifugal separation acconplishdinthat centrifugal. These steps of llixiiig`d` aldi gati are tial with the co1i'resflacnclingfstepsl oftheabove-Inentioned patont l to Aiiibisrsiidunderwood. u

Theaqueous'phenolate liquor discharged from centrifugal I3 is nekt passed to a` still I4, in Whiclfi` it is` concentrated; by evaporation of f a substantialproprtionoflthe Water content.-V The con'centratedsolutin -r uiting from this vaporatingfstepfis' next reacted with carbon dioxide to' effect springing of` asulostantial part' of the sodiin"phenolates,` and-:formation of sodium carbonate? 'Ilhsfresults"l precipitation ofthe phenolfsf f-ree vby the springingraction from solution' eauueousi pianse;` and' solution of the sodiurncaibate forrned by the springing reactionin'the aqueous phase.I The" springing reaction'mayA be accomplished by passingthe aqueous phenolate lp "aisedtvnviardly through the tower i-sjwiiiiopassingcarton dioxide upwardly into that tower; as wiii ooqweii understood bytnoso skiuodf tHe-art. '1n-e mixture-oi sodium car- 1ibei atioriofthe-ta acids; isn z ijexi passed to o .separator` I`li*,-Wl51i'ch` maybe either a. gravity or centif'ugal"sepf'irtor,1 tofeifect subsidence of the sodiun par] oonate" solution from the sprung ta'r acids;` So'di-ufnli`1`jv`coiride may be regenerated by caustinit/.ationF with liniewof the aqueous` sodium carbonatefslution dischargcdfr'om' the separator |65, and tlief resulting sodiuirihydroxide' solution may be used in the treatment of a further quan#- bona o'soltionwitiiuiooii phase, resulting `from tity of tar in the mixer I2, or for any other desired use.

The tar acid phase, discharged as a supernatant oil from the separator I6, is next passed to a mixer I'I Where it is mixed with sulfuric acid from tank I 8 to effect completion of the springing reaction and formation of sodium sulfate by reaction of the sulfuric acid with th'e phenolates.

This reaction results in the formation of a mixv ture consisting of an aqueous phase comprising principally sodium sulfate solution, and an oil phase containing liberated tar acids. This mixture is passed to a centrifugal separator I9 which effects continuous separation'of these two phases and separate discharge thereof.,

The tar acid phase discharged from the-centrifugal I9 contains practically no alkali, but still contains constituents which would resultv in the formation of a coke-like residue in the still if this tar fraction Were to be distilled without further intermediate treatment after discharge from the centrifugal I9. An important feature of the invention consists in the manner in which this coking incident to distillation is avoided.

The tar acid phase discharged from the centrifugal I 9 is passed to a mixer 28, where it is mixed with a naphthenic solvent from tank 2l. The mixing of the tar acid phase with the naphthenic solvent effects precipitation from solution of the constituents which would otherwise cause coking in the still, and these constituents can thereafter be removed from the tar acids by filtration in the filter 22. An excellent solvent for use in precipitating the undesired constituents (whichl will be referred to hereinafter in the specification and claims as coking constituents) is methylalcohol, and excellent results have been obtained in the practice of the invention in cases in which the tar acid phase discharged from the centrifugal I9 is mixed with twice its volume of methyl alcohol.

The tar acids discharged as a filtrate from the lter 22 may be passed to a, still 23, which may be of either the batch or continuous type, and subjected to distillation in that still to remove methyl alcohol from the tar acids and effect separation of tar acids from residual oil.

The invention has been described above in the simplest and preferred embodiment thereof. Various details may be modified without departing from the spirit of the invention. For example, the step of distilling off water in the still I4 may be entirely eliminated. The purpose of this step is two-fold. In the i'lrst place, the concentration of the phenolate fraction at this stage is desirable because of the fact that it improves the efciency of the salting outeffect on the tar acid compounds upon subsequent treatment with carbon dioxide In the second place, it is desirable that the sodium carbonate solution obtained from the vseparator I6 be relatively concentrated in order'to facilitate regeneration of sodium hy-` droxide therefromQand thisobject can Abe accomplished most efficiently by Aremoval of water from the phenolate fraction prior to the treatment thereof by carbonv dioxide Since neither of the above features of `advantage is absolutely essential to the successful performance of the process, however, the material discharged as an aqueous phase from thecentrifugal I3 may be treated with carbon dioxide in the tower' I5 without the performance of the intermediate distillation step stili la. f p

The step of effecting further springing of phe- Vsteps described above and illustrated in the attached flow sheet, a substantial part of the advantages of the invention may be accomplished .in spite of the omission of the springing and separating steps performed in tower I 5 and separator I6, or of the springing and separating steps performed in the elements II, I3 and I9 of the flow sheet. Thus, the advantages in avoiding passage of coking constituents to the still may be obtained in connection with' the use of naphthenic solvent as described in connection with reference numerals 20, 2I and 22 of the flow sheet, in cases in which carbon dioxide is used as the springing reagent and the acid springing step is eliminated,A` or in cases in which an acid alone is used as the springing reagent and the carbon dioxide springing is eliminated. It is desirable, however,`that both the carbon dioxide springing step and the acid springing step be performed prior to the step of precipitating coking constituents, since the performanceof the springing step with carbon dioxide affords an important advantage in that it results in the formation of sodium carbonate, which is much more Valuable than the sodium sulfate into which the sodium content of the phenolates would be converted if sulfuric acid alone-were used for springing. 'I'he acid treatment, after the carbon dioxide treatment also affords an important advantage in that a much more complete springing reaction and more effective removal of sodium compounds from the mixture can be accomplished by the inclusion of the acid springing step after the carbon dioxide springing, than can be accomplished if the acid springing step is eliminated.

While th'e step of precipitating coking constit.

uents in a form in which they can be removed; from the tar acid phase discharged from the cen-l trifugal I 9 has been described as performed by; the addition of methyl alcohol, it will be under-.Y` stood that other naphthenic solvents, such as; chloroform, carbon disulfide or sulfur dioxide may be employed in connection with the practice.- of this step of the invention.

While the treatment of the tar in the mixer |23 has been described as being performedby the; addition of sodium. hydroxide, it will be understood th'at equivalent alkaline reagents can be: substituted in this step. Potassium hydroxide, or any alkali capable of reacting with the tar; acids to form a soluble alkaliphenolate phase which may thereafter be separated from the tar by centrifugation, may, for example, be substituted for the sodium hydroxide used in this step.

Still further modifications will be obvious to those skilled in the art and I do not therefore wish to be limited except by thescope of the subjoined claims.v

I claim:

1. In the recovery of tar acids from Vtar the process comprising mixing the tar with an aqueous alkali metal hydroxide solution, separating phase from the tar by centrifugation, concentratbonate v`solution, trom theresultng tarracid phase. mixingthetar acid. phase, from which thealkali metal 'i carbonate solution has been separated. witha springing acid, separating the resulting liar acidphase 'from the resulting saltsolutionphase to obtain a tar'acid ,phase substantially freedof` salt solution, mixing' the tar .acid phase, from which saidgsalt solution phase hasbeen separated, with a solvent chosen from the class consistingl of' methyl alcohol, chloroform carbon disuldeand sulfur dioxide to effect precipitation of., coking constituents, thereafter 'removing said precipitated c'oking constituents from thesolution of` tar aci'ds 'in said solvent, 'and separatingthe solvent'and other impurities fromth'e' taracids by distillation.'

2;. In the rrecovery `of, tar acids from tar, the Presets cmprisns mixing .the tar with an aque- Qls. ellsali metal hydroxide solution, Separating the resulting aqueous alkali Vmetal phenolate Dhase from the tar ,by` centrifugation, concentrating the resulting aqueous alkali metal phenolate phase by evaporating Water therefrom, adding carbon dioxide to the concentrated phenoe late phase, separating the resulting alkali metal carbonate solution from the resulting tar acid phase, mixing the tar acid phase, from which the alkali metal carbonate solution has been separated, with sulfuric acid, separating the resulting tar acid phase from the resulting salt solution phase to obtaina tar acid phase substantially freed of salt solution, mixing the tar acid phase, from which said salt solution phase has been separated, with a solvent chosen from the class consisting of methyl alcohol, chloroform, carbon disulfide and sulfur dioxide to effect precipitation of coking constituents, thereafter removing said precipitated coking constituents from the solution of tar acids in said solvent and separating the solvent and other impurities from the tar acids by distillation.

3. In the recovery of tar acids from tar, the process comprising mixing the tar with an aqueous alkali metal hydroxide solution, separating the resulting aqueous alkali metal phenolate phase from the tar by centrifugation, mixing the resulting aqueous alkali metal phenolate phase with a springing acid, separating the resulting tar acid phase from the resulting salt solution phase and obtaining a tar acid phase substantially freed of salt solution, mixing the tar acid phase, from which said salt solution has been separated, with a solvent chosen from the class consisting of methyl alcohol, chloroform, carbon disulfide and sulfur dioxide to effect precipitation of coking constituents, thereafter removing said precipitated coking constituents from the solution of tar acids in said solvent and separating the solvent and other impurities from the tar acids by distillation.

4. In the recovery of tar acids from tar,'the process comprising mixing the tar with an aqueous alkali metal hydroxide solution, separating the resulting aqueous lalkali metal phenolate phase from the tar by centrifugation, adding carbon dioxide to said phenolate phase, separating the resulting alkali metal carbonate solution from the resulting tar acid phase and obtaining a tar acid phase substantially freed of salt solution, mixing the tar acid phase with a solvent chosen from the class consisting of methyl alcohctchlorcforn. disiiiiisieand .Sulfur dioisidefl.. r...ctn ,.tian oi taking @sustituents, thereafter removing said precipitate," olginslcohstitilehts frein the tahitien i .tar acids 5 mtas separating. .the solventahd e., `im!! .,tiesrircm the taratiis byttilla- "5.-" In the.. recgrerveiftar acids from phthalate .d by .extraction 0f tar with an 1o inetalhrdiaxide solution, the protce. adding carbon diQXide t0 'th-e tin. separating the resulting alkali .e `Soliititil from the resulting tar hase,mixing` the tar acid phase, from which 1 @animate tahitien' has been Sep- Sniihsine acid, Vseparating the re,- ffisitfithe1esi1-1.tins salt. S0- in, tar acid phase Substanltdsolution, mixing the tar acid altsolution phase has vent chosen from the g ,l Y alcohol, chloroform, ulde and 'sulfur dioxide to effect preip tion c'okin'g constituents,A Vthereafter remoying, said precipitated ckingA V"constituents from'"the'fslutiwoftar acids'in saidsolvent and separating the solvent and other impurities from the tar acids by distillation.

6. In the recovery of tar acids from phenolate solutions obtained by extraction of tar with an aqueous alkali metal hydroxide solution, the process comprising, adding carbon dioxide to the phenolate solution, separating the resulting alkali metal carbonate solution from the resulting tar -acid phase and obtaining a tar acid phase substantially freed of salt solution, mixing the tar acid phase, from which said salt solution phase has been separated, with a solvent chosen from the class consisting of methyl'alcohol, chloroform, carbon disulfide and sulfur dioxide to effect precipitation of coking constituents, thereafter removing said precipitated coking constituents from the solution of tar acids in said solvent and separating the solvent and other impurities from the tar acids by distillation.

'7. In the recovery of tar acids from phenolate solutions obtained by extraction of tar with an aqueous alkali metal hydroxide solution, the process comprising, mixing the phenolate solution with a springing acid, thereafter separating the resulting tar acid phase from the resulting salt solution phase to obtain a tar acid phase substantially freed of salt solution, mixing the tar acid phase, from which said salt solution phase has been separated, with a solvent chosen from the class consisting of methyl alcohol, chloroform, carbon disulfide and sulfur dioxide to effect precipitation of coking constituents, thereafter removing said precipitated coking constituents from the solution of tar acids in said solvent and separating the solvent and other impurities from the tar acids by distillation.

8. In the recovery of tar acids from phenolate solutions obtained by extraction of tar with an aqueous alkali metal hydroxide solution, the process comprising, mixing the phenolate solution with a springing acid, thereafter separating the resulting tar acid phase from the resulting salt solution phase to obtain a tar acid phase substantially freed of salt solution, mixing the tar acid phase, from which said salt solution phase has been separated, with a solvent chosen from the class consisting of methyl alcohol, chloroform, carbon disulfide and sulfur dioxide to 75 effect precipitation of coking constituents and thereafter removing said precipitated coking con-` stituents from the solution of tar acids in said solvent.

9. In the production of tar acids, the process comprising separating from tar a fraction consisting principally of tar acids, but containing constituents which cause a coke precipitate to form upon distillation, mixing said tar acid fraction with methyl alcohol to effect precipitation of said coking constituents, and thereafter separating the precipitated coking constituents from the resulting solution of tar acids in methyl alcohol.

10. In the production of tar acids, the process comprising separating from tar a fraction consisting principally of tar acids, but containing constituents which cause a coke precipitate to form upon distillation, mixing said tar acid fraction with a solvent chosen from the class consisting of methyl alcohol, chloroform, carbon disulfide and sulfur dioxide to eiect precipitation of said coking constituents from the solution of tar acids in said solvent, and thereafter separating said precipitated coking constituents from said solution.

11. In the recovery of tar acids from tar, the

process comprising mixing the tar with an aque# ous sodium hydroxide solution, separating the resulting aqueous sodium phenolate phase from the tar by centrifugation, concentrating the resulting aqeuous sodium phenolate phase by evaporating water therefrom, adding carbon dioxide to the concentrated phenolate phase, separating the resulting sodium carbonate solution from the resulting tar acid phase, mixing the tar acid phase from which the sodlium carbonate solution has been separated with sulphuric acid, separating the resulting tar acid phase from the resulting salt solution phase by centrifugal force to obtain a tar acid phase substantially free of salt solution, mixing the tar acid phase, from which said salt solution phase has been separated, with a solvent chosen from the class consisting of methyl alcohol, chloroform, carbon disulphide, and sulphur dioxide to effect precipitation of the coking constituents, thereafter filtering the resulting mixture to remove precipitated coking constituents from the solution of tar acids in said solvent and separating the solvent and other impurities from the tar acids by distillation. CHARLES M. AMBLER, JR. 

